Two of the Istari.
No names are given in the LotR, The Silmarillion or the Essay about the Istari in the Unfinished Tales, to the two wizards that went into the East; they are just called "IthrynLuin", the "BlueWizards".
In his annotations to this essay, Christopher Tolkien indicates that the BlueWizards are named Alatar and Pallando, and that they are associated with OromŽ, the Valar who possesses the most knowledge of the lands of Middle-earth. Christopher Tolkien also mentions a letter by J. R. R. Tolkien in which he discusses the Blue Wizards as "emissaries" to lands in the East and South under the yoke of Sauron--although he fears that they, like Saruman, failed.
According to another note - at the time of the presentation of the Unfinished Tales considered as "illegible" - but eventually read and presented in HoMeXII: "The Five Wizards" "the 'other two' came much earlier, at the same time probably as Glorfindel, when matters became very dangerous in the Second Age. Glorfindel was sent to aid Elrond and was (though not yet said) pre-eminent in the war of Eriador. But the other two Istari were sent for a different purpose. Morinehtar and Romestamo. Darkness-slayer and East-helper."
See also: FAQ/What are the names of the BlueWizards
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